PROJECT SUMMARY/ABSTRACT Vocal fold paralysis (VFP) occurs when the recurrent laryngeal nerve (RLN) is injured, most commonly during surgery of the neck. Bilateral injury to the RLN can result in potentially life-threatening airway obstruction and the need for tracheostomy. The RLN can regenerate some of its axons, but in many patients with paralysis some form of intervention is required to correct the airway obstruction and voice changes. This is most frequently achieved through reinnervation of the laryngeal muscles to restore function. Current practice is to wait 6-24 months before any intervention is performed as spontaneous recovery can occur. This delay before repair allows chronic changes in the nerve distal to the site of injury to occur and results in poor recovery. The overall goal of this proposal is to accelerate recovery after RLN injury and reduce the consequences of prolonged denervation before nerve graft. Previous work has focused mainly on events that occur late in the repair and remodeling process. Little is known about how manipulating events in the early stages of repair can be used to improve recovery. We have recently shown that modifying the type of macrophages accumulating at the graft site early after injury increases Schwann cell migration in the regenerative bridge and improves recovery. Our preliminary data demonstrate that a novel injectable medical device, Peripheral Nerve Matrix (PNM), can promote axon extension and Schwann cell migration across the site of nerve injury and promote functional recovery after injury. These preliminary data have been developed with optimal surgical conditions using a research grade material. In this proposal we determine the effects of a range of conditions that might be encountered in the operating room, particularly temperature, on polymerization of the gel and its ability to improve nerve repair. We then test the ability of PNM to improve outcomes after immediate and delayed nerve graft and assess local effects on protein expression, axon extension and Schwann cell migration. We then assess downstream effects on neuromuscular junction formation and peak tetanic force of the target muscle. For these experiments we use an animal model which is highly relevant to nerve graft repair of the RLN. The ability to accelerate recovery following RLN injury, by intervening intra-operatively, would reduce the consequences of delayed repair and improve recovery for patients with VFP.